Calculation on effective thermal conductivity of recycled aggregate thermal insulation concrete with added glazed hollow beads

In this paper, available structural models and equations for predicting the effective thermal conductivity (ke) of recycled aggregate thermal insulation concrete, including series, parallel, Maxwell-Eucken, eEffective medium theory, and Gong's model are discussed and extended to three phases by considering the effect of glazed hollow beads (GHBs). The solid porosity of GHBs is estimated and used in the equations. A unified model for calculating ke values is proposed, where the fractal dimension of GHBs is considered. A simple expression characterizing the fractal dimension of GHBs is derived. Nine batch specimens with different concrete mixtures are tested to determine the k e values which are compared with the predicted values. The predicted values from Unified-2 model are found to be in good agreement with the experimental results.